Clinical Scenario

A 67-year-old patient is scheduled for hip replacement surgery. He has heard that surgery can cause blood clots, and he wants to know how to reduce his chances of perioperative blood clots.

Clinical Question

For high-risk patients, does prophylaxis against venous thromboembolism (VTE) with the combined modalities of leg intermittent pneumatic compression (IPC) and pharmacologic prophylaxis provide more protection than either treatment alone?

Evidence-Based Answer

Based on high-quality evidence, the Cochrane review showed that combining IPC with pharmacologic prophylaxis was more effective than a single preventative measure for preventing deep venous thrombosis (DVT), and more effective than IPC alone for preventing pulmonary embolism (PE).1 (Strength of Recommendation = A, based on consistent and good quality patient-oriented evidence). The studies were not powered to detect a difference between combined and pharmacologic prophylaxis alone for the prevention of PE. Combined modalities should be used for orthopedic, urologic, cardiothoracic, gynecologic, or general surgeries.1

Cochrane Abstract

Background: It has been suggested that combined modalities are more effective than single modalities in preventing venous thromboembolism (VTE; defined as deep venous thrombosis [DVT] and pulmonary embolism [PE], or both) in high-risk patients.

Objectives: To assess the effectiveness of intermittent pneumatic compression (IPC) combined with pharmacologic prophylaxis versus single modalities in preventing DVT in high-risk patients.

Search Strategy: The authors searched the Peripheral Vascular Disease Specialized Register and the Cochrane Central Register of Controlled Trials (CENTRAL) for relevant studies. They also searched the reference lists of relevant articles to identify additional trials.

Selection Criteria: Randomized controlled trials (RCTs) and controlled clinical trials of combined IPC and pharmacologic interventions used to prevent VTE in high-risk patients. All patients in the trials selected were surgical or trauma patients.

Main Results: The authors identified 11 studies, six of which were RCTs. The trials included 7,431 patients. Compared with compression alone, the use of combined modalities reduced significantly the incidences of symptomatic PE (from about 3 to 1 percent; odds ratio [OR] = 0.39; 95% confidence interval [CI], 0.25 to 0.63) and DVT (from about 4 to 1 percent; OR = 0.43; 95% CI, 0.24 to 0.76). Compared with pharmacologic prophylaxis alone, the use of combined modalities significantly reduced the incidence of DVT (from 4.21 to 0.65 percent; OR = 1.6; 95% CI, 0.07 to 0.34), but the included studies were underpowered in regard to PE. The comparison of compression plus anticoagulant prophylaxis versus compression plus aspirin showed a nonsignificant reduction in PE and DVT in favor of the former group. Repeat analysis restricted to the RCTs confirmed the above findings.

Authors' Conclusions: Compared with compression alone, combined prophylactic modalities decrease significantly the incidences of PE and DVT. Compared with pharmacologic prophylaxis alone, combined modalities significantly reduced the incidence of DVT, but the effect on PE is unknown. The results of the current review support the use of combined modalities, especially in high-risk patients. More studies are needed on their role in PE prevention compared with pharmacologic prophylaxis alone.

These summaries have been derived from Cochrane reviews published in the Cochrane Database of Systematic Reviews in the Cochrane Library. Their content has, as far as possible, been checked with the authors of the original reviews, but the summaries should not be regarded as an official product of the Cochrane Collaboration; minor editing changes have been made to the text (http://www.cochrane.org).

Practice Pointers

Many hospitalized patients develop VTE, which can be fatal, can result in long-term disability from postphlebitic syndrome or loss of cardiopulmonary reserve, or can extend hospital stay. Almost all hospitalized patients have at least one risk factor for VTE, such as immobility, trauma, cancer, stroke, joint replacement surgery, spinal cord injury, or critical illness. Rates of asymptomatic DVT range from less than 10 percent in low-risk patients (e.g., those having minor surgery) to 40 to 80 percent in high-risk patients (e.g., those having hip or knee arthroplasty).2 Whereas many general surgery patients having open abdominal surgery are considered moderate risk (10 to 40 percent asymptomatic DVT), patients with cancer are considered high risk.2

High-risk surgery and trauma patients were studied in the 11 clinical trials included in this Cochrane review.1 The rate of symptomatic VTE was analyzed. No medical patients were included in the trials in this review.

There is considerable evidence that prophylaxis with mechanical devices (e.g., IPC) or anticoagulants (e.g., unfractionated heparin, low-molecular-weight heparin, warfarin [Coumadin], fondaparinux [Arixtra]) significantly reduces the risk of symptomatic and asymptomatic VTE. The initial evidence for the benefit of VTE prophylaxis was in surgical patients, but other studies have looked at high-risk medical patients, with similar results.3

The Cochrane review, using randomized controlled trials and controlled clinical trials, shows that VTE risk can be reduced further by combining IPC with pharmacologic prophylaxis.1 In hospitalized patients, sluggish venous blood flow, increased blood clotting, and blood vessel endothelial injury contribute to the development of VTE. The authors postulate that this greater risk reduction occurs because more than one of the etiologic factors for VTE is being treated. Aspirin alone modestly reduces risk, but is inferior to other pharmacologic modalities and is not recommended as a single agent.2 The Cochrane review shows that, as a combined modality, aspirin can be recommended, but is still likely inferior to IPC plus anticoagulant.1

Experts have emphasized that many cases of VTE are a result of omitted prophylaxis. For example, in one retrospective study, medical patients who developed DVT had received VTE prophylaxis 25.4 percent of the time compared with surgical patients with DVT who received prophylaxis 53.8 percent of the time.4 The underutilization of VTE prophylaxis extended to pharmacologic and mechanical modalities. The recent consensus statement from the American College of Chest Physicians strongly recommends that all hospitals have a formal, active policy to put this evidence into practice and address the prevention of VTE in hospitalized patients.2

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The Cochrane Abstract is a summary of a review from the Cochrane Library. It is accompanied by an interpretation that will help clinicians put evidence into practice. Dr. Meyer presents a clinical scenario and question based on the Cochrane Abstract, followed by an evidence-based answer and a critique of the review. The practice recommendations in this activity are available at http://www.cochrane.org/reviews/en/ab005258.html.

The series coordinator for AFP is Clarissa Kripke, MD, Department of Family and Community Medicine, University of California, San Francisco.